This invention relates broadly to lenses and polymeric materials useful in optic and ophthalmic arts. More specifically, this invention relates to a polymer composition useful in the manufacture of contact lenses. Still more specifically, this invention relates to contact lenses useful as extended-wear contact lenses.
In recent years, a wide variety of research has been carried out to develop polymeric materials useful for making extended-wear contact lenses which affect minimally corneal health and give wearers maximal comfort. Ideally, extended-wear contact lenses would display high oxygen permeability, high ion permeability, good wettability, adequate on-eye movement, and tear exchange, all of which are required to maintain corneal health and wear comfort.
There have been many attempts to prepare different polymers having different properties to make extended-wear lenses having some of the above-mentioned desired properties. For example, see U.S. Pat. Nos. 3,808,178; 4,136,250; and 5,070,169 and especially PCT publication WO9631792. In WO9631792, Nicolson et al. teaches a process and polymer composition for making extended-wear lenses having an oxygen transmissibility of at least 70 barrers/mm; an ion permeability characterized either by (1) an Ionoton Ion Permeability Coefficient of greater than about 0.2xc3x9710xe2x88x926 cm2/sec or (2) an Ionoflux Diffusion Coefficient of greater than about 1.5xc3x9710xe2x88x926 cm2/min. Extensive research is still carried out with the aim of developing new materials that are suitable for making extended-wear lenses that have minimal adverse effects on corneal health and wearer comfort.
An objective of the invention is to provide a composition that can make an ophthalmic lens having high water content, high ion permeability, an oxygen transmissibility of at least 57 barrers/mm, all of which are sufficient for corneal health and wearer comfort during extended periods of continuous wear.
Another objective of the invention is to provide an ophthalmic lens the surface of which is modified to increase wettability and thereby to increase further the wearer""s comfort.
A further objective of the invention is to provide an ophthalmic lens capable of extended continuous wear periods of at least 24 hours without substantial adverse impact on ocular health or consumer comfort, and more preferably, to provide a lens capable of continuous wear of 7 days or more without substantial adverse impact on ocular health or consumer comfort.
Yet another objective of the invention is to provide methods of forming an extended-wear ophthalmic lens.
The present invention is largely based on the discovery that a polymer composition, that is obtained by modifying the formulation of the polymer composition disclosed by Nicolson et al. (U.S. Pat. No. 5,849,811, herein incorporated by reference in its entirety), can be used to make extended-wear ophthalmic lenses. The lenses disclosed herein have a higher water content, higher ion permeability, and more adequate on-eye movement than those disclosed by Nicolson et al., while they still display an oxygen transmissibility of 57 barrers/mm or higher and are surface treated to optimize ocular compatibility.
It also has been discovered that unlike polymeric materials disclosed by Nicolson et al., the ion and/or water permeability of polymeric materials (or lenses) is not clinically effected by the presence of oxygen in polymerization reactions. Therefore, inert environments can be avoided in the manufacture of lenses. Therefore, lower cost for the production of lenses can be achieved by using a polymer composition of the present invention.
Such results are unexpected, because the polymer composition of the invention comprises a higher content of hydrophilic monomers which would be expected to decrease substantially the oxygen transmissibility of lenses.
The polymer composition of the invention comprises a macromer, a hydrophobic siloxane-containing monomer, and a hydrophilic monomer. The polymer composition of the invention is useful for making ophthalmic lenses which are suited to extended periods of wear in continuous, intimate contact with ocular tissue and tear fluid. The lens displays a balance of oxygen permeability and ion permeability sufficient to maintain good corneal health, adequate movement of the lens on the eye and wearer comfort during extended wear periods. The lens is formed by polymerization, preferably copolymerization. Preferably, the lens includes a core polymeric material and ophthalmically compatible surfaces. In a preferred embodiment, the surface is more hydrophilic and less lipophobic than the core polymeric material.
Another embodiment of the invention is a method of forming an ophthalmic lens having high oxygen permeability and high ion permeability. The method includes the step of forming a core material, having an inner surface and an outer surface, such that at least one pathway for ion transport and at least one pathway for oxygen transport are present from the inner to the outer surface. In a preferred embodiment, the method includes treating the surface of the lens to render the surface more hydrophilic than the core.
A further embodiment of the invention is an ophthalmic lens comprising a polymeric material which has a high oxygen permeability and a high ion or water permeability, the polymeric material being formed from the polymer composition of the invention. The lens displays a balance of oxygen permeability, ion permeability, water content and favorable modulus of elasticity, all of which sufficient to maintain good corneal health, adequate movement of the lens on the eye and wearer comfort during extended wear periods.
Yet another embodiment of the invention is a method of using a contact lens of the invention as an extended wear lens. The method includes (a) applying the lens to the ocular environment and (b) allowing the lens to remain in intimate contact with the ocular environment for a period of at least 24 hours without substantial adverse impact on corneal health or wearer comfort. A preferred method includes additional steps of (c) removing the lens from the ocular environment; (d) disinfecting the lens; (e) applying the lens to the ocular environment; and (f) allowing the lens to remain in intimate contact with the ocular environment for a period of at least an additional 24 hours. In a preferred embodiment, the lens is worn for a continuous period of at least 4 days without substantial adverse impact on corneal health or wearer comfort.